1. Field of the Invention
The present invention pertains to an audio line driver amplifier which is a high performance amplifier used to amplify voice and/or tones for driving 300 to 600 ohm balanced telephone lines with levels up to 20 DBM. The output of the amplifiers must be a very high impedance so that a number of amplifiers can bridge the telephone lines simultaneously at the same location without detrimental effects on the line termination.
2. DESCRIPTION OF THE PRIOR ART
Prior art line driver amplifiers have always been push-pull class A amplifiers with a high output impedance. However, because the quiescent current of the class A amplifiers is high, relatively large amounts of power are used and much heat is generated. To dissipate the heat generated by the large current drain of the amplifiers, relatively large heat sinks are required which severely limits the size of the amplifier.